Is it bad to ask guy I used to date why he lost interest in me?

As I was dating him we didn’t meet up so much, and he wouldn’t text me much. I found him online on tinder and broke it off with him. It’s been a month since then. I want to know why he lost interest. How bad is it if I ask? How can I ask in a tactful way?
Updates
1 y
To be honest I still want him
Updates
1 y
I want to ask him if he genuinely liked me
Is it bad to ask guy I used to date why he lost interest in me?
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